High School Biology-Chemistry SMILE Meeting
28 January 2003
Notes Prepared by Porter Johnson

SPECIAL OPENER

Roy Coleman made a presentation before the group--- in the spirit of Popeil-GinsuŽ
Knife Commercials. Using an electronic projector and laptop computer, he
showed us samples of the content of a CD containing all
information on the SMILE and SMART websites. But, wait;
there was more stuff on it!

All for just $10! And on a CD nicely packaged in a beautifully
labeled jewel case.

Then in a short ceremony of sorts, Roy also presented several long-term staff members
with cups bearing the inscription: Where's My CoffeeŽ
[Magic Coffee Happy Face Mug; Item No: 4706; ordered from The Johnson Smith
Company ([http://www.johnsonsmith.com/].
There are dark, frowning faces on the cup when it is empty,
and bright, smiling faces when the cup contains HOT coffee. Roy showed that
it was important to keep it filled with HOT
coffee, since the change is thermally activated. What a wonderful eye-opener! Thanks, Roy!

Pat Riley [Lincoln Park HS, Chemistry]
How Thick is a Piece of Aluminum Foil??
Pat had us separate into groups of about 4, and then gave each group the
following problem:

Task: Determine the thickness of Aluminum foil! Write down the
steps your team does in order to solve this problem.

Time: You have 20 minutes to solve the problem

Materials available to you:

box of Aluminum foil

scissors

metric ruler

balance

graduated cylinder

water

Chemistry textbook

There is more than one way to attack this problem. The following solutions were proposed:

Fold the foil over a number of times [and count how many times!], press
the folds flat so that there is no space between them, measure the
total thickness, and divide by the number of folds.

Cut a piece of foil, and measure its surface area and its mass M
. Then, fold it up, put it in the graduated cylinder partially filled with water, and
measure the volume V displaced by the compressed foil. Now, the density,
D, of
Aluminum foil of mass M, volume V, area A, and thickness t are related by

D = M / V = M / ( A t)

Solve to determine the foil thickness t.

Proceed as in the previous case, but use the density of Aluminum given in the
textbook (say, 2.699 g/cm3 at 20° C),
which would surely be more accurate than that determined in the rather difficult, imprecise
measurement of D in the previous step.

... and ... Did anybody who read the label on the foil box make use of
the information given there? Was this just 3 mil foil, [thickness
t = 0.075 cm] or what?

Good work, Pat!

Therese Donatello [St Edwards
Elementary School] The Nuts and Bolts of Chemical
Compounds Therese helped us understand chemical ions at a molecular level by using
various types nuts and bolts to model them. We divided into groups of
about 4, and she gave each group a set consisting of 4 nuts and four bolts. The nuts and bolts
all had the same diameter, but the bolts were of
various lengths. The length of a bolt represents its
"valence", corresponding to the maximum number of nuts that would fit
on the bolt. A bolt of "valence two" will hold two nuts, etc.
There were various types of nuts, with square heads [Sq] or
hexagonal heads [Hx]. We could use the symbol [Bo] to represent a short
bolt, as well as [Bl] to represent a long bolt. Then, the configuration with two
hexagonal nuts on a short bolt is represented by the
symbol [BoHx2], whereas with two square nuts it would be [BoSq2].

We could also "combine" the
bolts by having two short bolts to share the same hexagonal nut. This would
correspond to the combination [Bo2Hx], in our symbolic
notation. We could then use bolt combinations to model chemical
reactions. For example, the reaction [combination]

2 long bolts + 2 hex nuts ® 2-2
structure

could be represented symbolically as

2 Bl + 2 Hx ® Bl2 Hx2

Note
that, as an example, the "compound" Bo2Sq2
is represented by two
short
bolts attached with two square nuts, and similarly for other
configurations. We are limited as to what configurations we can make
with the types of bolts and nuts in question, and that reflects an intrinsic property of
the corresponding chemical compounds.